Clutch disc assembly

ABSTRACT

A clutch disc assembly interposed between an input side rotary member and an output side member has a hub, disc-like plates, a friction member, an elastic member and a viscous damper mechanism. The hub is connectable for co-rotation with the output side member. The hub has a flange on its outer circumference. The disc-like plates are rotatably mounted on the hub. The friction member is connected to said disc-like plates, for frictional engagement with the input side rotary member. The elastic member is for elastically connecting the flange and the disc-like plates whereby the flange and the disc-like plates are rotatable with respect to each other. The viscous damper mechanism includes a fluid medium, for displacing the fluid medium through restrictions in response to angular movements of the disc-like plates and the flange with respect to each other.

This is a divisional of U.S. patent application Ser. No. 08/144,682filed Oct. 28, 1993 now U.S. Pat. No. 5,590,752.

BACKGROUND OF THE INVENTION

The present invention relates to a clutch disc assembly used in avehicle.

The clutch disc assembly is interposed between an automotive engine andan automotive transmission. The clutch disc assembly is used to connector disconnect the power transmission and also to dampen torsionalvibration as a damper. In general, the clutch disc assembly includes ahub connectable to an input shaft of the transmission and having aflange on its circumference, a pair of disc-like plates rotatablymounted on the hub and disposed on both sides of the flange, frictionmembers fixed to the disc-like plates for frictional engagement with aninput side rotary member such as the engine flywheel, coil springs usedas elastic members for elastically coupling the disc-like plates and theflange in the circumferential direction, and a frictional resistancegeneration mechanism interposed between the disc-like plates and theflange.

In this clutch disc assembly, when torsional vibration is transmittedfrom the flywheel thereto, the coil springs are repeatedly compressedand expanded so that the pair of disc-like plates and the hub aretwisted relative to each other. During this angular movement of thedisc-like plates and the flange relative to each other, frictionalresistance is generated on the basis of the frictional resistancemechanism, to thereby dampen energy of the torsional vibration.

In such a clutch disc assembly, in order to effectively dampen thetorsional vibration over a wide operational range, it is preferable thatmagnitude of the frictional resistance be varied depending upon thekinds of the torsional vibration. There are two kinds of torsionalvibrations, for example, torsional vibration having small angulardisplacement caused by the combustion fluctuation of the engine, andlow-frequency torsional vibration having large angular displacementwhich is caused when a driver suddenly depresses or loosens anaccelerator pedal. In order to dampen the torsional vibration havingsmall angular displacement, the clutch disc assembly has to have lowrigidity/small resistance characteristics as a damper. In order todampen the low-frequency torsional vibration having large angulardisplacement, the clutch disc assembly has to have a high rigidity/largeresistance characteristics as a damper.

In the conventional clutch disc assembly, the two different torsionalcharacteristics may be realized by using a structure where the twodifferent frictional forces are generated depending on the differentkinds of the torsional vibration. However, with the frictionalresistance by the sliding movement of the frictional member, it would beimpossible to increase the second stage frictional force to asatisfactory level. It would be therefore impossible to sufficientlydampen the low-frequency vibration.

Recently, automotive vehicles have been widely used on highways. Thus,frequency of the engagement/disengagement of a clutch has beendecreasing because of more highway use. For this reason, when a servicelife of a clutch disc assembly as a whole is contemplated, a problem ofwear of friction facings has become less important. Then, a service lifeof an elastic member support portion of the pair of disc-like plates isbeing raised. In other words, when the torsional vibration is generated,the elastic member is repeatedly expanded and contracted to thereby wearthe support portion of the disc-like plates.

SUMMARY OF THE INVENTION

It is an object of the present invention to increase the resistance inorder to dampen the low-frequency vibration.

It is another object of the present invention is to decrease the wear ofthe disc-like plates due to the expansion/contraction of the elasticmembers.

A clutch disc assembly according to an aspect of the present inventionis interposed between an input side rotary member and an output sidemember; and comprises a friction member, disc-like plates, a hub, and aviscous damper mechanism.

The hub is connectable for co-rotation with said output side member andhas a flange on its outer circumference. The disc-like plates arerotatably mounted on the hub. The fiction member is connected to thedisc-like plates for frictional engagement with the input side rotarymember. The elastic member is for elastically connecting the flange andthe disc-like plates whereby the flange and the disc-like plates arerotatable with respect to each other. The viscous damper mechanismincludes a supply of viscous fluid medium and is for displacing thefluid medium through restrictions in response to angular movements ofthe disc-like plates and the flange with respect to each other.

In this clutch disc assembly, when the friction member is frictionallyengaged with the input side rotary member, the torque transmitted fromthe input side rotary member is transmitted from the friction member andthe disc-like plates to the flange of the hub through the elasticmember. When the torsional vibration is input from the input side rotarymember, the elastic member is repeatedly expanded/contracted between thedisc-like plate and the flange. At this time, the torsional vibration isdampened by the viscous resistance generated by the viscous dampermechanism.

The viscous damper mechanism generates the viscous resistance byutilizing the fluid medium. Thus, it is possible to increase theresistance to dampen the low-frequency torsional vibration.

In the foregoing operation, if the disc-like plates and the hub form afluid chamber containing fluid medium and the elastic member is disposedtherein, the wear of the disc-like plates is prevented by the fluidmedium to thereby prolong the service life of the clutch disc assembly.

The foregoing and other objects, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a clutch disc assemblyin accordance with the first embodiment of the invention;

FIG. 2 is a partially fragmentary plan view showing the clutch discassembly;

FIG. 3 is a partial perspective view showing an annular member;

FIG. 4 is an enlarged view of FIG. 2 and a view showing one operationalcondition of the viscous damper mechanism;

FIG. 5 is a view showing another operational condition showing theviscous damper mechanism; and

FIG. 6 is a view showing still another operational condition showing theviscous damper mechanism.

FIG. 7 is a partial longitudinal sectional view showing a clutch discassembly according to the second embodiment of the invention;

FIG. 8 is a partially fragmentary plan view showing the clutch discassembly;

FIG. 9 is a partially enlarged view of FIG. 8; and

FIG. 10 is a partially enlarged view of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIRST EMBODIMENT

FIGS. 1 and 2 show a clutch disc assembly in accordance with firstembodiment of the invention. The line 0--0 represents a rotarycenterline of the clutch disc assembly.

In the figures, the clutch disc assembly is composed mainly of a hubhaving a flange on its outer circumference, a clutch plate 3 and aretaining plate 4 which are disposed on both sides of the flange 2 androtatably fitted on the hub 1 from the outer circumferential sides, aplurality of coil springs 6 for elastically coupling both plates 3 and 4with the flange 2 in the circumferential direction, and a viscous dampermechanism 7 disposed within a fluid chamber 5 formed by both the plates3 and 4 and the hub 1, which generates viscous resistance during therelative rotation between both the plates(3,4) and the flange 2.

The hub 1 is, at its central portion, formed with spline teeth 1a forengagement with spline portions on an outer circumference of an inputshaft (output side member) of the transmission (not shown).

The fluid chamber 5 is filled with a fluid such as oil. The outercircumferential wall of the fluid chamber 5 is formed by an outercylindrical wall 4a extending in the axial direction from the retainingplate 4. An O-ring 29 is disposed between an edge flange of the outercircumferential cylindrical wall 4a and the clutch plate 3 to seal theouter circumferential portion of the fluid chamber 5. There are also aplurality of cushioning plates 31 fixed to the outer circumferentialportion of the clutch plate 3 by rivets 30. Frictional facings 9 arefixed to both sides of the cushioning plates 31 to be pressed against aflywheel (not shown). Sealants 8 are attached between the innercircumferential portions of the clutch plate 3 and the retaining plate4, and the outer circumferential surfaces of the hub 1, respectively, toseal the inner circumferential portion of the fluid chamber 5.

As shown in FIG. 2, sector-like cutaways 2a opening radially outwardlyare formed in the outer circumferential portion of the flange 2. Coilsprings 6 are received into the spring seats 6a provided at both ends ofeach cutaway 2a. The coil spring 6 is arranged within the cutaway 2asuch that intervals between the adjacent coil turns on the radiallyoutward side are larger than those on the radially inward side. Supportportions 3b and 4b are each tapered radially inward, sector-like, andaligned with the intervals between the cutaways 2a. These supportportions 3b and 4b are in contact with the spring seats 6a of the coilsprings 6.

The viscous damper mechanism 7 is disposed radially inwardly from thecoil springs 6. The viscous damper mechanism 7 is composed mainly of apair of annular members 12, rectangular plate-like fixed members 13fixed to the flange 2, and a pair of sliders 15 disposed within arcuatechambers 14 (see FIGS. 2 and 3) formed in the annular members 12. Eachof the pair of annular members 12, as shown in FIG. 3, has an opening inthe inward axial directions with respect to the whole device (upwardlyin FIG. 3). The plurality of arcuate chambers 14 are formed by aplurality of partition portions 12a which are formed at a constantinterval in the circumferential direction. A cutaway 12c is formed in aninner circumferential wall at the central portion of each chamber 14.The cutaway 12c extends into a part of a side wall of the chamber 14.The pair of annular members 12 are fixed to the clutch plate 3 and theretaining plate 4 by stud pins 16 at the partitioning portions 12a. Thestud pins 16 are inserted into long holes(not shown) formed in thecircumferential direction of the flange 2. The long holes formed in theflange 2 ensures that the chambers 14 facing each other through theflange 2 communicate with each other.

The fixed members 13 extend in both axial directions of the flange 2 andare disposed in the respective arcuate chambers 14. The sliders 15 whichare in the form of boxes are disposed at both ends of the fixed members13 in the axial direction. Inner and outer walls of the sliders 15 havesubstantially the same shape of the outer and inner walls of the arcuatechambers 14 within which the sliders 15 lie so that they may be movablein the circumferential direction within the arcuate chambers 14 anddivides the arcuate chambers into two large partition chambers 20 and21, as shown in FIG. 4. Inside of the sliders 15 are divided into smallpartition chambers 18 and 19 by the fixed members 13. End walls of theslider 15 keep away from both the circumferential sides of the fixedmember 13 with a given displacement angle. Holes 15a are formed in bothend walls of the sliders 15 in the circumferential direction. Thus, thelarge partition chambers 20 and the small partition chambers 18 are incommunication with each other, and the small partition chambers 19 andthe large partition chambers 21 are in communication with each other.

The cutaways 12c of the annular members 12 substantially correspond to aneutral position of the sliders 15. In the neutral position, thecutaways 12c are in communication with all the small partition chambers18 and 19, and the large partition chambers 20 and the 21.

The operation of the clutch disc assembly and characteristics of theoperation will be described.

When the friction facings 9 are depressed against, for example, theengine flywheel, the torque of the engine flywheel is input to theclutch plate 3 and the retaining plate 4. The torque is transmitted tothe flange 2 of the hub 1 through the coil springs 6, and furthertransmitted to the input shaft (not shown).

The change in torsional rigidity of the coil springs 6 will beexplained. Assume that the hub 1 is fixed to a base (not shown) and theclutch plate 3 and the retaining plate 4 is twisted relative to thehub 1. When the plates 3 and 4 start the torsional operation relative tothe flange 2 (hub 1), mainly, the outer circumferential side of the coilsprings 6 will flex to obtain a low rigidity characteristics. When thecompression of the coil springs 6 is developed, the innercircumferential side of the coil springs 6 starts to be compressed toobtain a high rigidity characteristics. After the stud pins 16 have beenbrought into contact with ends of the long holes of the flange 2, theangular movement of the clutch plate 3 and the retaining plate 4 to theflange 2 is finished.

During the above-mentioned torsional operation, the viscous resistanceis generated by the viscous damper mechanism 7. Assume that the clutchplate 3 and the retaining plate 4 are twisted, for example, in directionR₁, from the neutral position shown in FIG. 4. In this case, the annularmembers 12 and the sliders 15 are rotated together in the rotationaldirection R₁. Thus, the small partition chambers 19 in the sliders 15are compressed to be small in volume, and at the same time, the smallpartition chambers 18 are expanded to be large in volume. At this time,the fluid will flow radially out from the small partition chambers 19through the cutaways 12c of the annular members 12 and into the smallpartition chambers 18 through the cutaways 12c, wherein said cutaways12c opening to the small partition chambers 19 functions as a firstchoke portion. Since the cross-sectional area of the flow paths of thecutaways 12c is formed to be large, the viscous resistance is small.Accordingly, in this case, the small viscous resistance is generated.

After the torsional angle is increased so that the circumferential wallson the rear side of the sliders 15 in the circumferential direction arebrought Into contact with the fixed member 13 (FIG. 5), the largepartition chambers 21 is contracted to be small in volume, and the largepartition chambers 20 is expanded to be large in volume. At this time,at first, the fluid will flow from the large partition chambers 21through the cutaways 12c. When the torsional operation is advanced, asshown in FIG. 6, the communication between the second large partitionchambers 21 and the cutaways 12c is interrupted by the sliders 15. As aresult, the fluid contained in the large partition chambers 21 will notflow through the cutaways 12c so that the fluid contained in the largepartition chambers 21 will be pressured to flow through the holes 15aand further to seep inbetween intimate interfaces between the sliders 15and the fixed members 13, wherein the intimate interfaces function assecond choke portions. Since the flow path area of the intimateinterfaces as the second choke portion is small, the viscous resistanceis large.

In the case where the clutch plate 3 and the retaining plate 4 arereturned on the side R₂ after they have been twisted on the side R₁,first of all, the rear ends of the sliders 15 in the circumferentialdirection are separated away from the fixed members 13, and the fluidwill flow from the cutaways 12c into the small partition chambers 19.When the sliders 15 are kept on returning to the side R2, the fluid willflow from the cutaways 12c into the large partition chambers 21.Consequently, when the components are returned once they have beentwisted, the fluid quickly returns back to the partition chambers wherethe fluid has been compressed after angular movements. Accordingly, thereturn operation of the twist operation may be smoothly and quicklyattained. Incidentally, when the rear ends of the sliders 15 separatefrom the fixed members 13, all the partition chambers are incommunication with the cutaways 12c so that a small viscous resistanceis generated.

Assume that torsional vibration having a small angular displacement istransmitted to the viscous damper mechanism 7 due to, for example,combustion fluctuations of the engine under the condition that theclutch plate 3 and the retaining plate 4 are in the neutral position asshown in FIG. 4. In this case, the annular member 12 and the slider 15move relative to the flange 2 in a small-angle range, whereby the fluidgoes in and out from the small chambers 18 and 19 through the firstchoke portion formed by the cutaways 12c. Therefore, small viscousresistance effectively dampens the torsional vibration having a smallangular displacement.

Further assume that the torsional vibration having a small angulardisplacement is transmitted to the viscous damper mechanism 7 under thecondition that the clutch plate 3 and the retaining plate 4 are twistedrelative to the flange 2 through a certain angle. In this case, theannular member 12 and the sliders 15 move relative to the flange 2 in asmall-angle range where the first and second small partition chambers 18and 19 are in fluid communication with the cutaways 12c, so that it ispossible to obtain a small viscous resistance. Namely, the time when theviscous resistance is changed is not determined by the absolute twistangle of the clutch plate 3 and the retaining plate 4 relative to theflange 2 but by the positional relation between the sliders 15 and thefixed members 13.

Assume that the low-frequency torsional vibration is input to theviscous damper mechanism 7 because the driver suddenly depresses orloosen the accelerator pedal. Since the low-frequency torsionalvibration has a large angular displacement, the annular member 12 movesrelative to the flange 2 in a large angle range where the fluid in thelarge partition chambers 20 and 21 mainly flows into the small partitionchambers 18 and 19 through the holes 15 and the intimate interfacesbetween the fixed member 13 and the slider 15, which generates largeviscous resistance.

In this case, since the viscosity of fluid is utilized, it is possibleto generate a large viscous resistance in comparison with the frictionalresistance by the conventional friction member. Accordingly, it ispossible to effectively dampen the low-frequency torsional vibration.

As mentioned before, the viscous damper mechanism 7 can effectivelydampen two different kinds of torsional vibrations by generatingdifferent magnitudes of the viscous resistance. Also, by the utilizationof the viscosity, the change of the torsional rigidity may be smooth.

The viscous damper mechanism 7 is disposed radially inwardly of the coilspring 6, and hence it does not suffer the enlargement of the clutchdisc assembly as a whole.

The coil springs 6 are lubricated within the fluid chambers 5.Therefore, even if the coil springs 6 are repeatedly expanded andcompressed and might be brought into contact with the support portions3b and 4b of the clutch plate 3 and the retaining plate 4, frictionalwear and damage at the support portions 3b and 4b would hardly occur. Asa result, the service life of the clutch disc assembly as a whole may beimproved.

SECOND EMBODIMENT

FIGS. 7 and 8 show a clutch disc assembly in accordance with the secondembodiment of the present invention. The line 0--0 represents a rotarycenterline of the clutch disc assembly.

In the figures, the clutch disc assembly is composed mainly of a hub 101having a flange 102 on its outer circumference, a clutch plate 103 and aretaining plate 104 which are arranged on both sides of the flange 102and rotatably mounted on the hub 101 from the lateral sides, first coilsprings 106 and second coil springs 107 for elastically coupling bothplates 103 and 104 with the flange 102 in the circumferential directionwithin a lubrication chamber 105 defined by both plates 103 and 104 andthe hub 101, and a viscous damper mechanism 108 disposed within thelubrication chamber 105 for generating viscous resistance by utilizingthe lubricant oil contained in the lubrication chamber 105 during therelative rotation of both the plates 103 and 104 to the flange 102. Thehub 101 has, at its inner side, spline teeth 101a for engagement withspline portions on an outer circumference of the input shaft (outputside member) of the transmission (not shown).

The lubrication chamber 105 is filled with fluid such as grease orlubricant oil. A bush 109 is used to center the clutch plate 103 and toseal an inner circumferential portion of the lubrication chamber 105.The retaining plate 104 has, on its outer circumferential portion, acylindrical wall 104a extending toward the clutch plate 103 and incontact with the latter. An O-ring 110 is disposed between the clutchplate 103 and a flange portion of the cylindrical wall 104a to seal theouter circumferential portion of the lubrication chamber 105. Also, aplurality of cushioning plates 111 are fixed to the outercircumferential portion of the clutch plate 103 by rivets 112.Frictional facings 113 are fixed to both sides of the cushioning plates111. When the friction facings 113 are depressed on, for example, anengine flywheel (input side rotary member not shown), the torque isinput to the clutch disc assembly.

The clutch plate 103 and the retaining plate 104 are coupled with eachother at the inner circumferential portion by first pins 115 and at theouter circumferential portion by second pins 116.

Three first window holes 102a and three second window holes 102b,smaller than the first window holes 102a in both the circumferentialdirection and radial direction, are formed alternatively in radiallymiddle portions of the flange 102. The first pins 115 are inserted intoan inner peripheral portion of the first window hole 102a. When thefirst pins 115 are brought into contact with edges of the first windowholes 102a in the circumferential direction, the torsion between theclutch plate 103 and retaining plate 104 to the flange 102 (and the hub101) is restricted. Large diameter double coil springs 106 and smalldiameter double coil springs 107 are disposed within the first windowholes 102a and the second window holes 102b, respectively. It should benoted that each of the double coil springs 106 and 107 is formed by alarge diameter coil spring and a small diameter coil spring insertedinto the respective large diameter coil spring. A predetermined intervalis provided between spring seats 106a located at both ends of eachspring 106 and the first window hole 102a. Spring seats 107a provided atboth ends of the second coil spring 107 are brought into contact withboth ends of the second window hole 102b in the circumferentialdirection. Drawing portions 103b, 104b and 103c are formed at theportions of both the plates 103 and 104 corresponding to the first coilsprings 106 and the second coil springs 107 for receiving them.

The viscous damper mechanism 108 is disposed further radially outwardlyof the coil springs 106 and 107. As shown in FIGS. 9 and 10, the viscousdamper mechanism 108 is composed of an annular member 118 having aplurality of arcuate chambers 119 which have a long hole open radiallyinwardly and extending circumferentially, projections 102c projectingradially outward from outer edge of the flange 102 and inserted into thearcuate chambers 119 of the annular member 118 through the long hole,and cap-shaped sliders 120 disposed movably in the circumferentialdirection of the arcuate chamber 119.

The annular member 118 is composed of two halves 118a divided in theaxial direction and is interposed on the inner circumferential side ofthe cylindrical wall 104a between the clutch plate 103 and the outercircumferential portion of the retaining plate 104. The second pins 116(see FIG. 7) pass through the two halves 118a which form the annularmember 118. Thus, the annular member 118 is rotated together with theclutch plate 103 and the retaining plate 104. As described above and asshown in FIG. 10, the parts corresponding to the arcuate chambers 119 ofthe annular members 118 are U-shaped with the long hole opening radiallyinwardly. The outer edge of the flange 102 is inserted into the longhole of the arcuate chamber 119, whereby the annular member 118 and theflange 102 can rotate relative to each other. The fluid filled in thechambers 119 is the same as the lubricant oil or grease used in thelubrication chamber 105. Engagement projections 118b each extendinginwardly are formed on the inner circumferential edges of the twomembers 118a of the annular member 118 and the engagement projections118b are engaged with annular grooves 102d provided on both sides of theouter circumferential portion of the flange 102 to thereby seal theinner circumferential portion of the arcuate chamber 119.

Shape of the outer circumferential wall of the slider 120 corresponds toshape of the wall of the arcuate chamber 119 so that the slider 120 canmove smoothly in the arcuate chamber 119. The arcuate chamber 119 isdivided into large chambers 123 and 124 by each slider 120. The largechambers 123 and 124 are in fluid communication with a small chamber 121and a small chamber 122 through cutaway portions formed radiallyinwardly of both sides of stopper portions 120a, respectively.

The projection 102c of the flange 102 is inserted into the each slider120 so that the interior of the slider 120 is divided into the smallchambers 121 and 122. The small chambers 121 and 122 are in fluidcommunication with each other through a first choke C₁ between theprojection 102c and the inner circumferential surface of the slider 120.The slider 120 has the stopper portions 120a keeping away from theprojection 102c through a certain angle in the neutral position. Thecutaway portion made in the stopper portion 120 is larger in size thanthe first choke C₁. When the slider 120 is moved in the circumferentialdirection and brought into contact with the projection 102c, the cutawayportion is closed. A second choke C₂ which is smaller than the firstchoke C₁ is kept between the outer circumferential wall of the sliderand the inner circumferential wall of the arcuate chamber 119.

A first side plate 126 and a second side plate 127 are disposed on bothsides of the flange 102 within the lubrication chamber 105. The firstand second side plates 126 and 127 are coupled with the clutch plate 103and the retaining plate 104 in an elastic manner in the circumferentialdirection through the first springs 106, and coupled with the flange 102in an elastic manner in the circumferential direction through lowrigidity coil springs 129. As shown in FIG. 8, abutment portions 127a tobe brought into contact with the spring seats 106a of the first coilsprings 106 are formed on the outer circumferential plate of the secondside plate 127 (This is the case with respect to the first side plate126 too).

Third window holes 102e are formed on an inner circumferential side ofeach second window holes 102b in the flange 102. The low rigidity coilspring 129 is disposed in the third window hole 102e. Spring seats 129aare provided at both ends of the coil spring 129. The spring seats 129aare extending in the axial direction and are brought into contact withboth ends in the circumferential direction of each hole formed in thefirst and second side plates 126 and 127.

The first and second side plates 126 and 127 are coupled with each otherby stopper pins 130 which are coupled with each other at the innercircumferential portion. The stopper pins 130 pass through fourth windowholes 102f formed in the inner circumferential portion of the flange102. A predetermined gap is kept in the circumferential directionbetween the stopper pins 130 and the fourth window holes 102f. When thestopper pins 130 are brought into contact with both ends in thecircumferential direction of the fourth window holes 102f, the torsionalmotion is restricted between the first and second side plates 126 and127 to the flange 102. A flange portion 109a of the bush 109 is arrangedbetween the first side plate 126 and the flange 102. Disc plates 132,133 and 134 are interposed between the flange 102 and the second sideplate 127.

A first disc plate 135 is disposed between the inner circumferentialportion of the clutch plate 103 and the first side plate 126, and asecond disc plate 136 is disposed between the second side plate 127 andthe retaining plate 104. A hole 136a (FIG. 8) extending in thecircumferential direction is formed in the first disc plate 135 and thesecond disc plate 136 so that the stopper pins 130 are movable in thecircumferential direction.

The operation of the clutch disc assembly and the characteristics of theoperation will be described.

When the friction facings 113 are depressed against, for example, theengine flywheel, the torque of the engine side flywheel is input intothe clutch plate 103 and the retaining plate 104. The torque istransmitted through the first coil springs 106, the second coil springs107 and the low rigidity coil spring 129 to the flange 102 of the hub101 and further to the shaft on the output side.

The change in torsional rigidity between the clutch plate 103 and theretaining plate 104 to the flange 102 will be explained.

Assume that the hub 101 is fixed to a base (not shown) and the clutchplate 103 and the retaining plate 104 are twisted to the flange 102(thehub 101). When the clutch plate 103 and the retaining plate 104 starttorsional motion, the lowest rigidity coil springs 129 are compressed.When the stopper pins 130 are brought into contact with one of both endsin the circumferential direction of the fourth windows 102f of theflange 102, the relative rotation between the side plates 126 and 127 tothe flange 102 is finished. When the compression of the first coilsprings 106 is developed, then, the clutch plate 103 and the retainingplate 104 cause the second coil springs 107 to be compressed.Thereafter, it is possible to obtain the high rigidity characteristics.When the first pins 115 are brought into contact with one of both endsin the circumferential direction of the first window holes 102c of theflange 102, then, the relative movement of both the plates 103 and 104to the flange 102 is finished.

In the foregoing torsional operation, the viscous resistance isgenerated mainly by the viscous damper mechanism 108 in addition to theslippage among the bush 109 and the disc plates 132 to 134 clamped thatare between the side plates 126 and 127 and the flange 102 and also tothe slippage between the first and second plates 135 and 136 clampedbetween the clutch plate 103 and the retaining plate 104 and the sideplates 126 and 127.

In the foregoing torsional operation, assume that the clutch plate 103and the retaining plate 104 are displaced in, for example, a rotationaldirection R₁ from the neutral point shown in FIG. 9. The annular member118 and the sliders 120 are moved together in the rotational directionR₁. As a result, the small chambers 122 within the sliders 120 arecompressed to be small in size, and at the same time, the small chambers121 is expanded to be large in size. Then, the lubricant oil within thefirst small chambers 121 will flow into the small chambers 122 throughchokes C₁ and also will flow through cutaway portions of the stoppers120a on the R₁ side to the large chamber 124. Since the cross-sectionalarea of the flow path of the choke C₁, is large, the viscous resistanceis small.

When the torsional angle is increased, and the stopper portions 120a onthe R₂ side are brought into contact with the projections 102c, the flowof the lubricant oil is stopped between the inside of the sliders 120and the projections 102c. Thus, the sliders 120 are held in a conditionthat the sliders 120 are fixed to the projections 102c. When thetorsional motion is further continued, the annular member 118 is movedin the rotational direction R₁. The large chambers 124 are compressed tobe small in size, whereas the large chambers 123 are expanded to belarge in size. The lubricant oil contained within the large chambers 124will then flow into the large chambers 123 through the choke C₂ betweenthe inner circumferential wall of the annular member 118 and the outercircumferential wall of the sliders 120. At this time, the flow patharea of the choke C₂ is small, the viscous resistance is large.

When the clutch plate 103 and the retaining plate 104 are returned afterthe clutch plate 103 and the retaining plate 104 have been twisted inthe R₁ direction, first of all, the stoppers 120a on the R₂ side of thesliders 120 are separated from the projections 102c so that choke C₁functions. For this reason, small viscous resistance is generated.

Assume that torsional vibration having a small angular displacement istransmitted to the viscous damper mechanism 108 due to, for example,combustion fluctuations of the engine under the condition that theclutch plate 103 and the retaining plate 104 are in the neutral positionas shown in FIG. 9. In this case, the annular member 118 and the slider120 reciprocally move relative to the flange 102 in a small-angle range,whereby the lubricant oil flows through the first choke C1. Therefore,small viscous resistance effectively dampens the torsional vibrationhaving the small angular displacement.

Further assume that the torsional vibration having the small angulardisplacement is transmitted to the viscous damper mechanism 108 underthe condition that the clutch plate 103 and the retaining plate 104 aretwisted relative to the flange 102 through a certain angle. In thiscase, the annular member 118 and the sliders 120 reciprocally moverelative to the flange 102 in small-angle range where the lubricant oilflows through the first choke C₁, so that it is possible to obtain smallviscous resistance. Namely, the time when the viscous resistance ischanged is not determined by the absolute twist angle of the clutchplate 103 and the retaining plate 104 relative to the flange 102, but bythe positional relation between the sliders 120 and the projection 102c.

Assume that the low-frequency torsional vibration is input to theviscous damper mechanism 108 because the driver suddenly depresses orloosen the accelerator pedal. Since the low-frequency torsionalvibration has a large angular displacement, the annular member 118reciprocally moves relative to the flange 102 in a large angle rangewhere the lubricant oil flows mainly through the second choke C₂, whichgenerates large viscous resistance.

In this case, since the viscosity of fluid is utilized, it is possibleto generate a larger viscous resistance in comparison with thefrictional resistance by the conventional friction member. Accordingly,it is possible to effectively dampen the low-frequency torsionalvibration.

As mentioned before, the viscous damper mechanism 108 can effectivelydampen two different kinds of torsional vibrations by generatingdifferent magnitudes of the viscous resistance. Also, due to utilizationof the viscosity, the change of the torsional rigidity may be smooth.

Also, since the viscous damper mechanism 108 is located most outwardlywithin the lubrication chamber 105, it is possible to generate a largehysteresis torque with a small resistance force to thereby make thedamper mechanism 108 compact.

Since the first coil springs 106 and the second coil springs 107 arelubricated within the lubrication chamber 105, even if these springs 106and 107 are repeatedly compressed and expanded, there is almost no fearthat frictional wear or damage would be caused in the drawing portions103b and 104b of the clutch plate 103 and the retaining plate 104. Thus,the service life of the clutch disc assembly is prolonged.

Various details of the invention may be changed without departing fromits spirits nor its scope. Furthermore, the foregoing description of theembodiments according to the present invention is provided for thepurpose of illustration only, and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

What is claimed is:
 1. A clutch disc assembly comprising:a hub having aflange on its outer circumference; a disc-like plate rotatably mountedon said hub, said disc-like plate at least partially defining a fluidchamber which is filled with a fluid medium; a friction member connectedto said disc-like plate; an elastic member located in said fluid chamberfor elastically connecting said flange and said disc-like plate for alimited rotary displacement relative to each other; a viscous dampermechanism disposed in said fluid chamber, having:an annular memberconnected to said disc-like plate and disposed radially outwardly ofsaid elastic member within said fluid chamber, said annular memberdefining a plurality of arcuate chambers, each of said arcuate chambersbeing sealed from adjacent ones of said arcuate chambers such that nofluid may flow between adjacent ones of said arcuate chambers; aplurality of sliders, each of said sliders having opposing abuttingportions, each one of said sliders being disposed in a corresponding oneof said arcuate chambers and being displaceable in circumferentialdirections; a plurality of stop members connected to said flange andeach of said stop members extended into a corresponding one of saidarcuate chambers and a corresponding one of said sliders, an insideportion of each of said sliders being divided by said stop members intotwo first chambers, and said sliders dividing said arcuate chambers intotwo second chambers; a first choke formed between each corresponding oneof said stop members and said sliders; a second choke formed between aninner wall of each of said arcuate chambers and said sliders an amountof fluid flow through said second choke being smaller than that of saidfirst choke; and said first choke being opened in response to afirst-angle of relative rotary displacement between said disc-likeplates and said flange so that said fluid medium flows through saidfirst choke, generating a first viscous resistance, and said first chokeportion being closed in response to a second-angle of relative rotarydisplacement between said disc-like plates and said flange which islarger than said first-angle so that said fluid medium flows throughsaid second choke, generating a second viscous resistance higher thansaid first viscous resistance.
 2. A clutch disc assembly according toclaim 1, wherein said viscous damper mechanism is located radiallyoutward of said flange, inner circumferential side of said arcuatechamber is formed with a hole extending circumferentially, outer edge ofsaid flange being inserted into said arcuate chamber through said hole,said stop member being a protrusion extending radially outward fromouter edge of said flange, outer circumference of said flange beingformed with annular grooves on the lateral sides, and said annularmember having sealing portions on the radially inner side which areinserted into said annular grooves.
 3. A clutch disc assembly accordingto claim 2, wherein said slider is a cap-like member covering saidprotrusion protruding radially outward, said cap-like member havingouter circumferential wall corresponding to a shape of an inner wall ofsaid arcuate chamber, said abutting portions extending radially inwardfrom ends of said outer circumferential wall, said abutting portionhaving a fluid path which is larger than said first choke portion and isclosed when said abutting portion of said slider and said protrusioncome into contact with each other, wherebysaid first choke portion is agap between said protrusion and said outer circumferential wall of saidcap-like member, and said second choke portion is a gap between saidinner wall of said arcuate chamber and said outer circumferential wallof said cap-like member.
 4. A clutch disc assembly according to claim 3,further comprising a sub plate in said fluid chamber, and said elasticmember is composed of a first elastic member elastically connecting saiddisc-like plates and said sub plate in the circumferential direction anda second elastic member elastically connecting said sub plate and saidhub in the circumferential direction, said second elastic member havingsmaller rigidity than said first elastic member.
 5. A clutch discassembly according to claim 4, wherein said first and second elasticmembers are coil springs extending circumferentially.
 6. A clutch discassembly comprising:a hub having a flange on its outer circumference; adisc-like plate rotatably mounted on said hub, said disc-like plate atleast partially defining a fluid chamber which is filled with a fluidmedium; an elastic member located in said fluid chamber for elasticallyconnecting said flange and said disc-like plate for a limited rotarydisplacement relative to each other; a viscous damper mechanism disposedin said fluid chamber, having:an annular member connected to saiddisc-like plate and disposed radially outwardly of said elastic memberwithin said fluid chamber, said annular member defining a plurality ofarcuate chambers, each of said arcuate chambers being sealed fromadjacent ones of said arcuate chambers such that no fluid may flowbetween adjacent ones of said arcuate chambers; a plurality of sliderseach of said sliders having opposing abutting portions, each one of saidsliders being disposed in a corresponding one of said arcuate chambersand being displaceable in circumferential directions; a plurality ofstop members connected to said flange and each of said stop membersextended into a corresponding one of said arcuate chambers and acorresponding one of said sliders, an inside portion of each of saidsliders being divided by said stop members into two first chambers, andsaid sliders dividing said arcuate chambers into two second chambers; afirst choke formed between each corresponding one of said stop membersand said sliders; a second choke formed between an inner wall of each ofsaid arcuate chambers and said sliders, an amount of fluid flow throughsaid second choke being smaller than that of said first choke; and saidfirst choke being opened in response to a first-angle of relative rotarydisplacement between said disc-like plates and said flange so that saidfluid medium flows through said first choke, generating a first viscousresistance, and said first choke portion being closed in response to asecond-angle of relative rotary displacement between said disc-likeplates and said flange which is larger than said first-angle so thatsaid fluid medium flows through said second choke, generating a secondviscous resistance higher than said first viscous resistance.
 7. Adamper disc assembly according to claim 6, wherein said viscous dampermechanism is located radially outward of said flange, innercircumferential side of said arcuate chamber is formed with a holeextending circumferentially, outer edge of said flange being insertedinto said arcuate chamber through said hole, said stop member being aprotrusion extending radially outward from outer edge of said flange,outer circumference of said flange being formed with annular grooves onthe lateral sides, and said annular member having sealing portions onthe radially inner side which are inserted into said annular grooves. 8.A damper disc assembly according to claim 7, wherein said slider is acap-like member covering said protrusion protruding radially outward,said cap-like member having outer circumferential wall corresponding toa shape of an inner wall of said arcuate chamber, said abutting portionsextending radially inward from ends of said outer circumferential wall,said abutting portion having a fluid path which is larger than saidfirst choke portion and is closed when said abutting portion of saidslider and said protrusion come into contact with each other,wherebysaid first choke portion is a gap between said protrusion andsaid outer circumferential wall of said cap-like member, and said secondchoke portion is a gap between said inner wall of said annular chamberand said outer circumferential wall of said cap-like member.
 9. A damperdisc assembly according to claim 8, further comprising a sub plate insaid fluid chamber, and said elastic member is composed of a firstelastic member elastically connecting said disc-like plates and said subplate in the circumferential direction and a second elastic memberelastically connecting said sub plate and said hub in thecircumferential C₁ and also will flow through cutaway portions of thestoppers direction, said second elastic member having smaller rigiditythan said first elastic member.
 10. A damper disc assembly according toclaim 7, wherein said first and second elastic members are coil springsextending circumferentially.